High-dose chemotherapy with autologous stem cell support is the current standard procedure in the first-line treatment in younger patients with myeloma fit for intensive treatment. Current practice in Switzerland for stem cell mobilization is the combination of chemotherapy and G-CSF stimulation in myeloma patients fit for high-dose chemotherapy with melphalan and autologous stem cell transplant. In this trial the intravenous application of Plerixafor is being investigated in respect of the capability of the mobilization of stem cells from the bone marrow into the peripheral blood. In contrast to the twice daily application of G-CSF (eg. Neupogen) for several days, Plerixafor has to be injected just one-time.